Charles Leclerc knocked team-mate Sebastian Vettel off the top of the timesheets to go fastest on a dominant opening day of practice for Ferrari ahead of the Formula One Belgian Grand Prix.
The Monegasque, who completed a one-two for the Maranello-based squad behind Vettel in the opening session, ended the day with a time of one minute, 44.123 seconds.
That lifted him 0.630 seconds clear of the Friday morning pace setter.
Valtteri Bottas, confirmed alongside Lewis Hamilton at Mercedes for another year on Thursday, was the Ferrari pair's closest challenger in third with the Briton hot on his heels in fourth.
The two silver cars, who between them have won 10 of this season's 12 races, improved from fifth and sixth in the morning but were still nearly a second off Leclerc's benchmark.
Hamilton in particular had a less than straightforward day, with throttle and telemetry problems in the opening session and then pitted to change helmets in the afternoon after complaining of dirt and dust coming through his visor.
Ferrari, still hunting for their first win of the year, have struggled around twisty tracks this season.
But their car has been better suited to high-speed layouts like Spa, which will host Sunday's race.
That track and Monza, where Ferrari’s home Italian Grand Prix will be held the week after, have been singled out as the two best opportunities for the team to shine.
Vettel is hoping that can help him win his first race in more than a year, with the German last tasting success in the 2018 edition of the Belgian Grand Prix.
Behind the top four, Sergio Perez was a strong fifth for Racing Point. However, the Mexican was forced to pull over with smoke and flames spewing out of the back of his car in the dying minutes.
The incident brought out the red-flag and an early end to the session.
Max Verstappen was sixth for Red Bull. The Dutchman, cheered on by his orange-clad fans, had been third in the opening session but the 21-year-old, winner of two of the last four races, complained of problems with his Honda power unit.
Kimi Raikkonen, nursing a pulled leg muscle that had prompted his Alfa Romeo team to put reserve driver Marcus Ericsson on standby, ended the day seventh ahead of Racing Point’s Lance Stroll.
Daniel Ricciardo, one of six drivers carrying engine-related grid penalties, was ninth for Renault.
Thai rookie Alexander Albon, fourth in the morning on his Red Bull debut, rounded out the top ten. Pierre Gasly, demoted from Red Bull to Toro Rosso in a swap with Albon, endured a difficult day finishing 17th.
The day was largely incident-free, with the most dramatic moment coming in the opening session when Stroll’s Racing Point shed some of its body work at high speed.
